Weather Conditions#
This section focuses on local and regional weather conditions for 2023, and compares these values to historical conditions. We’ll take a close look at monthly average air temperatures and precipitation. We will also look more closely at significant storms systems during the fall months.
Air Temperatures and Precipitation#
The maps below show temperature anomalies and percent of normal precipitation for western Canada in October. In general, most of British Columbia experienced drier than normal and slightly warmer than normal conditions this month. This follows a trend we’ve experienced since the beginning of the spring. We’ll focus more on Metro Vancouver in the following plots.
Fig. 5 Temperature Anomalies for Western Canada in October#
Fig. 6 Percent of Normal Precipitation for Western Canada in October#
The plot below shows the average monthly air temperature at the Lower Capilano Weather Station. Values for 2023 are show with the red or blue tick marks. The boxplot shows the median (line), first and third quartiles (box), and the range of max and min (whiskers). You will also see the monthly temperature anomaly displayed on the right. As we can see, the spring and summer months were very warm, and temperatures have remained slightly above normal in September and October.
The next plot shows monthly accumulated precipitation at the same weather station. Again, values for 2023 are displayed with the green (wetter than average) or red (drier than average) ticks. The summer season kicked off early with an exceptionally dry May. Conditions remained relatively dry throughout the summer. Several strong storms in mid-October pushed monthly rainfall amounts to near-normal.
Monthly Temperature and Precipitation Table
The table below shows monthly average air temperature and precipitation data for the Lower Capilano Watershed.
Month |
Mean Temp (°C ) |
Temp Anomaly (°C ) |
Precip (mm) |
Precip % Normal |
|---|---|---|---|---|
January |
3.5 |
+0.8 |
318 |
68 |
February |
1.8 |
-1.0 |
333 |
142 |
March |
4.2 |
-0.5 |
118 |
36 |
April |
6.2 |
-1.2 |
313 |
159 |
May |
15.3 |
+3.4 |
19.5 |
16 |
June |
15.9 |
+1.3 |
41 |
46 |
July |
19.3 |
+1.5 |
44 |
83 |
August |
18.8 |
+1.1 |
55 |
77 |
September |
14.3 |
+0.2 |
100 |
59 |
October |
9.7 |
+0.5 |
299 |
92 |
Air Temperatures#
The plot below shows the average daily temperature for 2023 (red line) compared to normals (gray shaded area) and the range of max and min (blue shaded area). New high and low temperature records are also plotted with red and blue dots. The sudden change in temperatures at the end of April is very clear. There is also an abrupt shift to cool temperatures in late October, with two new daily low temperature records set on October 27 and 28.
Hottest Day of the year
The hottest recorded temperature this summer was on August 13th. The daytime high reached 35.3 degrees in the Coquitlam Watershed
Precipitation#
The plot below shows the accumulated precipitation in the Lower Capilano Watershed in 2023. Last year is also shown in dark blue, and other years between 2003 and 2021 are shown with lighter shades of blue. Average annual accumulated precipitation is shown with the black dashed line.
The winter was marked by near normal precipitation, with the heaviest rain in February and the first half of April. It was an exceptionally dry spring, and remained dry throughout the summer. Between April 24 and September 30, only 260 mm of rain fell in the lower Capilano Watershed, which is less than 50% of normal for this period. Much needed rain came as a series of atmospheric rivers in mid-October. We’ll look more closely at these storms below.
Perhaps a better way to look at precipitation totals is to use the water year, which runs from October 1 to September 30. This captures the precipitation that falls in the autumn and early winter. Click on the dropdown below to see the 2023 water year. This was a very dry year (red line). The previous water year (2022) was exceptionally wet despite very dry conditions at the end of the water year. 2015 is also highlighted to show how important snow is to our water supply. This year was actually slightly wetter than average for most of the year, and finished as one of the wettest of the past 20 years. It was a lack of seasonal snow that made 2015 such a challenging year from a water supply perspective.
Annual Precipitation - Water Year 2023
This plot shows the accumulated precipitation during the 2023 water year. It was an exceptionally dry year. The only drier year was 2009, which was the selected analog year for 2023.
Dry Spells!
The longest dry spell of the year was 33 days (May 7 - June 9)
October was relatively dry to start and end, but it was very wet in the middle of the month. Two potent atmospheric rivers (AR) impacted the BC South Coast on Oct. 17-18, and 19-20. The second storm was rated as an AR 4, which is a very strong (bordering on extreme) atmospheric river. Fortunately, the duration of the AR was not exceptionally long. Fortunately there was no snow in the mountains when this storm rolled through. The one-day rainfall amount of 109.5 mm on October 19th was the highest daily rainfall total since the Christmas/Boxing Day storm last year.